Apparatus, computer medium, and method for embedding and extracting a first and second data into a watermark

ABSTRACT

In an information processing system having a plurality of information processing apparatuses connected through a network, at least one of the plurality of information processing apparatuses can add first additional information to input information as an electronic watermark using a first adding method, and can add second additional information to the input information as an electronic watermark using a second adding method. The first adding method has a higher robustness than the second adding method, and the first additional information can be used for identifying the second adding method.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to information processing systems,information processing apparatuses, and computer-readable recordingmedia used in the systems or the apparatuses, suited to cases in whichelectronic-watermark information is embedded in input information, suchas digital image data or digital sound data, to protect copyright, toprevent forgery, and to record various types of information.

2. Description of the Related Art

As computers and networks have been remarkably developed in recentyears, various types of information, such as character data, image data,and sound data, have been handled in the computers and networks. Sincesuch data is digital, it can be easily copied with its qualitymaintained. Therefore, to protect the copyright of such data, copyrightinformation and user information are embedded in image data and sounddata as electronic-watermark information (hereinafter just called anelectronic watermark) in many cases.

With the use of an electronic-watermark technology, information whichpeople cannot recognize with their senses of sight and hearing isconfidentially embedded in image data or sound data. When an embeddedelectronic watermark is extracted from image data or sound data,copyright information, user information, and identification informationare obtained, and illegitimate copying-can be traced.

A first condition required for such an electronic watermark is a qualityat which embedded information cannot be identified, namely, at whichinformation is embedded in the original digital information such thatthe quality of the original digital information does not deteriorate.

A second condition is robustness with which information embedded in theoriginal digital information remains, namely, with which embeddedinformation is not lost even if editing, such as data compression andfiltering, or an attack is applied.

A third condition is the amount of information to be embedded, which canbe selected according to use.

These conditions, required for electronic watermarks, are generallytradeoffs to each other. When an electronic watermark having a highrobustness is generated, for example, relatively large qualitydeterioration occurs and the amount of information to be embeddedbecomes small in many cases.

Methods for embedding electronic watermarks in multi-valued stillpictures can be divided into two types, spatial-domain embedding methodsand frequency-domain embedding methods.

In each of various electronic-watermark embedding methods, embeddingprocessing corresponds to extracting processing one by one, and there isno compatibility. In general, it is said that spatial-domain embeddingmethods provide low quality deterioration with low robustness, whereasfrequency-domain embedding methods provide high robustness withrelatively high quality deterioration. Each method has a differentfeature, such as a high robustness with a small amount of embeddedinformation, or a high quality with a low robustness.

To protect embedded information, information (hereinafter called a key)indicating algorithm, embedding positions, and changes are keptconfidential in many cases. This is to enhance robustness to anintentional attack in which the algorithm and embedding positions areanalyzed to remove electronic watermarks.

It can be considered to efficiently protect copyright that a monitoringorganization for checking whether illegitimate copying is performed, byextracting electronic watermarks is provided. It is important for such amonitoring organization to keep the electronic-watermark method used andthe key confidential to avoid an intentional attack.

As described above, there are various electronic-watermark methods eachhaving its own features. There are also many companies and associationswhich want to prevent illegitimate copying and illegitimate outputtingof digital data by the use of electronic watermarks. If such companiesand associations independently select electronic-watermark methods toembed electronic watermarks in data, since embedding processing andextracting processing correspond one by one in each ofelectronic-watermark methods and they are not compatible, the followingproblems occur.

1. It is difficult for one monitoring organization to perform unitedchecking because electronic-watermark extracting processing is neededfor each method.

2. To perform united checking by one monitoring organization, themonitoring organization needs to have all electronic-watermarkextracting techniques, causing a large load.

3. The monitoring organization needs to manage the keys corresponding toall the extracting techniques confidentially and strictly.

4. When a monitoring organization is provided for each method, if anembedded electronic watermark cannot be extracted, it cannot bedetermined whether the embedded electronic watermark has been generatedby a different method, or whether the electronic watermark has beenbroken by an attack.

One monitoring organization refers to one configuration in terms of asystem or a method, determined by standardization or a nation, ratherthan one physical organization.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to efficientlyprotect copyrighted materials in various electronic-watermark methods.

The foregoing object is achieved in one aspect of the present inventionthrough the provision of an information processing system in which aplurality of information processing apparatuses are connected through anetwork, at least one of the plurality of information processingapparatuses including first adding means for adding first additionalinformation to input information by a first adding method; and secondadding means for adding second additional information to the inputinformation by a second adding method, wherein the first adding methodhas a higher robustness than the second adding method.

The foregoing object is achieved in another aspect of the presentinvention through the provision of an information processing system inwhich a plurality of information processing apparatuses are connectedthrough a network, at least one of the plurality of informationprocessing apparatuses including first extracting means for extractingfirst additional information from input information by a firstextracting method; and second extracting means for extracting secondadditional information from the input information by a second extractingmethod identified by the extracted first additional information.

The foregoing object is achieved in still another aspect of the presentinvention through the provision of an information processing apparatusincluding first adding means for adding first additional information toinput information at a high robustness by a first adding method; andsecond adding means for adding second additional information to theinput information by a second adding method.

The foregoing object is achieved in yet another aspect of the presentinvention through the provision of an information processing apparatusincluding first extracting means for extracting first additionalinformation from input information by a first extracting method; andsecond extracting means for extracting second additional informationfrom the input information by a second extracting method identified bythe extracted first additional information.

The foregoing object is achieved in still yet another aspect of thepresent invention through the provision of an information processingmethod including a first adding step of adding first additionalinformation to input information at a high robustness by a first addingmethod; and a second adding step of adding second additional informationto the input information by a second adding method.

The foregoing object is achieved in a further aspect of the presentinvention through the provision of an information processing methodincluding a first extracting step of extracting first additionalinformation from input information by a first extracting method; and asecond extracting step of extracting second additional information fromthe input information by a second extracting method.

The foregoing object is achieved in a still further aspect of thepresent invention through the provision of a computer-readable recordingmedium for storing a program, the program including a first adding stepof adding first additional information to input information at a highrobustness; and a second adding step of adding second additionalinformation to the input information.

The foregoing object is achieved in a yet further aspect of the presentinvention through the provision of a computer-readable recording mediumfor storing a program, the program including a first extracting step ofextracting first additional information from input information; anidentifying step of identifying an extracting method by the extractedfirst additional information; and a second extracting step of extractingsecond additional information from the input information by theidentified extracting method.

Other objects and other features of the present invention will becomeclear by the following figures and descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a portion related to electronic-watermarkembedding in an information processing system according to a firstembodiment of the present invention.

FIG. 2 is a block diagram of a portion related to electronic-watermarkextracting in the information processing system according to the firstembodiment of the present invention.

FIG. 3 is a block diagram of a portion related to electronic-watermarkembedding in an information processing system according to a secondembodiment of the present invention.

FIG. 4 is a block diagram of a portion related to electronic-watermarkextracting in the information processing system according to the secondembodiment of the present invention.

FIG. 5 is a block diagram of a portion related to electronic-watermarkextracting in an information processing system according to a thirdembodiment of the present invention.

FIG. 6 is a block diagram of a portion related to electronic-watermarkembedding and extracting in an information processing system accordingto a fourth embodiment of the present invention.

FIGS. 7A and 7B are block diagrams of an electronic-watermark embeddingapparatus and an electronic-watermark extracting apparatus,respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

FIG. 1 shows a portion related to electronic-watermark embedding in aninformation processing system according to a first embodiment of thepresent invention. This system uses a common electronic-watermark methodand electronic-watermark methods unique to monitoring organizations. Thecommon electronic-watermark method refers to an electronic-watermarkmethod determined by standardization or related organizations, and thefeatures thereof will be described later.

In FIG. 1, organizations 101 to 104 perform electronic-watermarkembedding processing with the use of different electronic-watermarkmethods. In the organizations 101 to 104,common-electronic-watermark-embedding apparatuses 105 performelectronic-watermark embedding processing by the predetermined commonelectronic-watermark method, and a type-A-electronic-watermark embeddingapparatus 106, a type-B-electronic-watermark embedding apparatus 107, atype-C-electronic-watermark embedding apparatus 108, andtype-D-electronic-watermark embedding apparatus 109 performelectronic-watermark embedding by electronic-watermark methodsindependently determined by the organizations 101 to 104, respectively.A network 110 connects the organizations. The organizations 101 to 104have communication means, not shown, for connecting to the network 110.

The common electronic-watermark method, which thecommon-electronic-watermark embedding apparatuses 105 use, has thefollowing features.

1. Implements high-robustness electronic watermarks with a relativelysmall amount of information.

2. Extracts electronic watermarks without keys or with a common key.

3. Embeds information which identifies at least eachelectronic-watermark method or the organization which has performedembedding by the use of the method.

4. Has robustness to electronic-watermark embedding performed by eachorganization.

5. Sets a variable level of robustness in steps or continuously by thedecision of each organization and attaches data indicating a robustnessstrength to information in which electronic watermarks are embedded, asadditional information.

Various electronic-watermark methods having the foregoing methods can beconsidered. A method having a high robustness will be taken below asexample.

FIG. 7A shows an electronic-watermark embedding apparatus for performingthe above-described embedding processing, and FIG. 7B shows anelectronic-watermark extracting apparatus for performing theabove-described extracting.

When a still picture is input as input data serving as a copyrightedmaterial, the image data of the still picture is divided intoeight-by-eight-pixel blocks and discrete cosine transform (DCT) isapplied to each block. Hereinafter, a DCT-transformed block is called aDCT coefficient block, one coefficient in a DCT coefficient block iscalled a DCT coefficient, and a set of DCT coefficient blocks for onesheet of picture is called a DCT coefficient block group.

In the electronic-watermark embedding apparatus shown in FIG. 7A. animage transform unit 701 applies DCT to an input image “x” and theoutput of the image transform unit 701, a DCT coefficient block group,is input to an electronic-watermark embedding unit 702. Theelectronic-watermark embedding unit 702 selects one DCT coefficientblock to be embedded among the input DCT coefficient block group, andquantizes one DCT coefficient in the DCT coefficient block to embed oneembedding bit.

The size of a quantization step corresponds to the intensity ofembedding, and the size of the quantization step and the position of theselected DCT coefficient correspond to key information.

As an example, the value of a DCT coefficient located at the coordinates“u” and “v” is called s{u, v}, a quantization step is called “h,” and anelectronic-watermark bit of 0 or 1 is embedded by the following rule.ah<s{u, v}≦(a+1)h  (1)

The following operation is executed, and a coefficient used afterembedding is set to c{u, v}.c{u, v}=bh+h/2 for an embedding bit of 0  (2)where b is whichever of “a” and (a+1) is even.c{u, v}=bh+h/2 for an embedding bit of 1  (3)where b is whichever of “a” and (a+1) is odd.

Lastly, an inverse-image-transform unit 703 applies inverse DCT to theblock group to change it back to eight-by-eight-pixel blocks andreconstructs them. Then, an image “y” in which the electronic watermarkhas been embedded is obtained.

In the present embodiment, a setting unit 706 for variably setting thesize of a quantization step and/or an embedding position to variablyspecify a robustness strength is provided. This setting unit sets theabove factors according to various parameters such as a security level,automatically or by a manual operation of a person who monitors.

Data indicating the specified robustness strength is attached to theoriginal data as additional information at a subsequent stage of theinverse-image-transform unit 703. According to this data, an extractingoperation is specified at an extracting side.

The additional information may be common among the organizations, or maybe encrypted so that a third party cannot obtain the robustnessstrength.

To extract the electronic watermark in the electronic-watermarkextracting unit shown in FIG. 7B (1), the image “y” is input to an imagetransform unit 701, (2) an electronic-watermark extracting unit 705selects a DCT coefficient which has been embedded with key informationamong a DCT a coefficient block group to which the same DCT is applied(3), “b” which satisfies the following expression is obtained, and when“b” is even, it is determined that the embedding bit is 0, and when “b”is odd, it is determined that the embedding bit is 1:bh<c{u, v}≦(b+1 )h  (4)

A method for enhancing the robustness in this embedding method will bedescribed below.

When a DCT coefficient indicating a low-frequency component is selectedfrom a DCT coefficient block as a DCT coefficient to be embedded, therobustness is made strong. This is because, whereas high-frequencycomponents are likely to be lost due to image compression or varioustypes of filtering processing, low-frequency components are unlikely tobe lost.

In the above embedding method, one DCT coefficient block is selected andone DCT coefficient is embedded. The number of DCT coefficient blocks tobe selected and the number of DCT coefficients to be embedded can beincreased to enhance the robustness. When only one DCT coefficient isembedded for one bit, it is highly possible that the value of the bit islost due to image compression and various types of filtering processing.When the identical bits are embedded in a plurality of DCT coefficients,it is not highly possible that most of them are lost.

The robustness can be enhanced by applying error-correcting encoding tobits to be embedded themselves. This is because, even if some of theembedded bits are lost, they are recovered by an error-correcting code.It is clear that the robustness becomes stronger when the usederror-correcting code has a higher error-correcting capability. Althoughthe above techniques enhance the robustness, they may changelow-frequency components of an image, or the quality of the image maydeteriorate since many bits are embedded. Since identical bits areembedded with the use of many DCT coefficients, a small number of bitsare embedded in many cases. If an inverse operation is performed, therobustness becomes weaker, but image quality is satisfactory and a largeamount of information can be embedded in an electronic-watermark method.

The robustness-strength setting unit 706 may change the robustnessstrength by shifting an embedding position from a high-frequency side toa low-frequency side, or by changing the number of items to be embedded.

The above-described techniques for enhancing the robustness have thesame tendency not only for methods employing DCT but also for methodsemploying wavelet transform or Fourier transform and methods fordirectly manipulating the luminance of a pixel.

An embedding procedure will be described below by referring to FIG. 1.For simplicity, 00, 01, 10, and 11 are embedded by the commonelectronic-watermark method, which are two-bit information foridentifying the organizations 101 to 104. It is clear that other typesof information can be embedded.

Each of the organizations 101 to 104 embeds the bit corresponding toeach organization in distributed data by the common electronic-watermarkmethod which has the above-described features 1 to 5 and has a highrobustness with-the use of the common-electronic-watermark embeddingapparatus 105. Then, other types of information are embedded with theuse of the type-A to type-D electronic-watermark embedding apparatuses106 to 109 unique to the organizations. When the commonelectronic-watermark method does not interfere with anelectronic-watermark method unique to an organization, namely, whenelectronic-watermark embedding processing does not affect the commonelectronic-watermark information, the embedding order can be reversed.In each organization, a different piece of information may be embedded.Alternatively, the same information may be embedded. Each organizationcan embed various types of information, such as copyright information,user information, and identification information.

FIG. 2 shows a portion related to electronic-watermark extracting in thefirst embodiment.

In FIG. 2, there are provided a united monitoring organization 200, andelectronic-watermark monitoring organizations 201 to 204 correspondingto the organizations 101 to 104 shown In FIG. 1, respectively. Theunited monitoring organization 200 has a common-electronic-watermarkextracting apparatus 205 corresponding to thecommon-electronic-watermark embedding apparatus 105, and theorganizations 201 to 204 include a type-A-electronic-watermarkextracting apparatus 206, a type-B-electronic-watermark extractingapparatus 207, a type-C-electronic-watermark extracting apparatus 208,and a type-D-electronic-watermark extracting apparatus 209 correspondingto the type-A to type-D electronic-watermark embedding apparatuses 106to 109 shown in FIG. 1, respectively. A network 210 connects theorganizations 201 to 204. The organizations 201 to 204 havecommunication means, not shown, for connecting to the network 210. Thenetwork 210 may be identical with the network 110 shown in FIG. 1.

An electronic-watermark extracting procedure to be executed in FIG. 2will be described below.

The united monitoring organization 200 monitors data distributed or usedin the network 210. If data which seems to be an illegitimate copy isfound or reported on the network, the monitoring organization 200extracts information embedded by the common electronic-watermark method,by the use of the common-electronic-watermark extracting apparatus 205.With this operation, the organization which embedded the information orthe used method is identified, and the data is sent to the identifiedorganization.

The organization which receives the data extracts various types ofembedded information, by the use of the electronic-watermark extractingapparatus thereof, which is either of the type-A to type-Delectronic-watermark extracting apparatuses 206 to 209.

According to the present embodiment, even in a system which usesdifferent electronic-watermark methods in a mixed way, each organizationonly needs to manage an embedding section and an extracting section forits own electronic-watermark method, without preparing embeddingsections and extracting sections for many electronic-watermark methods.Illegitimate copying is efficiently monitored.

Even when an electronic watermark is not found, safety is enhanced forthe following reasons. If electronic-watermark information is not found,it is difficult to differentiate among whether the data does not includeelectronic-watermark information from the beginning, whether anelectronic watermark has been embedded by another method, and whetherelectronic-watermark information is broken by an attack. Since thecommon electronic-watermark method has a high robustness, it isdifficult for an attack to break electronic-watermark informationgenerated by the method.

Therefore, when electronic-watermark information generated by the commonelectronic-watermark method is extracted in a first process, apossibility of not having electronic-watermark information from thebeginning is eliminated. An electronic-watermark method unique to eachorganization may be used. When detailed information is embedded, a largeamount of information is embedded and an electronic-watermark methodhaving a relatively low robustness with suppression of qualitydeterioration being the focus is used in many cases. Therefore, afterelectronic-watermark information generated by the commonelectronic-watermark method is extracted, when electronic-watermarkinformation generated by the electronic-watermark method unique to eachorganization is not found, it can be said that electronic-watermarkinformation has been broken by an attack.

Therefore, overall safety has been improved by this system, as comparedwith a case in which each organization independently uses a uniqueelectronic-watermark method.

In the present embodiment, four organizations are included. It is clearthat the present invention can also be applied in the same way to asystem having any number of organizations.

(Second Embodiment)

FIG. 3 shows a portion related to electronic-watermark embedding in aninformation processing system according to a second embodiment of thepresent invention. In the present embodiment, only acommon-electronic-watermark embedding organization 300 uses the commonelectronic-watermark embedding apparatus 105 for embedding.

Organizations 301 to 304 only have the type-A to type-Delectronic-watermark embedding apparatuses 106 to 109, which use theunique electronic-watermark methods. The organizations 301 to 304 areformed by removing the common-electronic-watermark embedding apparatuses105 from the organizations 101 to 104 shown in FIG. 1. A network 110connects the organizations 301 to 304.

A united copyright management organization, such as Japanese Society forRight of Authors, Composers and Publishers (JASRAC) for musicalcopyrighted materials, can serve as the common-electronic-watermarkembedding organization 300. Sales shops which sell the users copyrightedmaterials controlled by the common-electronic-watermark embeddingorganization 300 can serve as the organizations 301 to 304. The presentembodiment does not limit cases to which the present invention isapplied. The present invention includes all techniques in which thecommon-electronic-watermark method having a high robustness and anelectronic-watermark method unique to each organization are usedaccording to conditions.

The organizations 301 to 304 (including each copyright holder) registercopyrighted materials at the organization 300 and ask it to executeembedding with the use of the common-electronic-watermark embeddingapparatus 105. The organization 300 embeds predetermined information bythe common electronic-watermark method, and sends back data to theorganizations 301 to 304. The organizations 301 to 304 use the type-A totype-D embedding apparatuses 106 to 109, which employ the uniqueelectronic-watermark methods, to embed various types of information.

The present embodiment has the following advantages over the firstembodiment.

In the first embodiment, since each organization performs embedding bythe common electronic-watermark method, the common electronic-watermarkmethod and its key need to be made public to each organization. It isbetter to keep the common electronic-watermark method and its keyconfidential for safety. If even one organization leaks information, theentire safety cannot be maintained. In the present embodiment, however,since the common electronic-watermark method does not need to be madepublic to the organizations 301 to 304, safety is enhanced.

The present embodiment can be combined with the first embodiment. When,in FIG. 3, the organizations 301 and 302 have the commonelectronic-watermark embedding apparatuses 105 in the same way as in thefirst embodiment, for example, the organizations 303 and 304, which donot have the common electronic-watermark apparatus 105, performs thesame processing as in the present embodiment, and the organizations 301and 302, which have the common electronic-watermark apparatuses 105, canembed the predetermined information by the common electronic-watermarkmethod within their organizations, as in the first embodiment.

FIG. 4 shows a portion related to electronic-watermark extracting in theinformation processing system according to the second embodiment.

In FIG. 4, a united monitoring organization 400 includes thecommon-electronic-watermark extracting apparatus 205, corresponding tothe common-electronic-watermark embedding apparatus 105, and the type-Ato type-D electronic-watermark extracting apparatuses 206 to 209,corresponding to the type-A to type-D electronic-watermark embeddingapparatuses 106 to 109 which employ the electronic-watermark methodsunique to the organizations. A network 210 connects to the organizations301 to 304, although they are not shown in FIG. 4. Instead of theorganizations 301 to 304, the organizations 101 to 104 may be connectedto the network 210. An electronic-watermark extracting procedure to beexecuted in FIG. 4 will be described below.

The organization 400 monitors data distributed or used in the network210. If data which seems to be an illegitimate copy is found or reportedon the network, the organization 400 extracts information embedded bythe common electronic-watermark method, by the use of thecommon-electronic-watermark extracting apparatus 205. With thisoperation, the organization which embedded the information or the usedmethod is identified. Then, various types of embedded information areextracted by the use of the extracting apparatus which employs theelectronic-watermark method unique to the identified organization.

In the system according to the present embodiment, only the unitedmonitoring organization can monitor illegitimate copying. Such a unitedmonitoring organization can be implemented if a finite number ofelectronic-watermark methods unique to organizations are used. Since theelectronic-watermark method unique to each organization is identified bythe common electronic-watermark method, it is not necessary to check anelectronic watermark with the electronic-watermark method unique to eachorganization by trial and error, and therefore the system is efficient.

The united monitoring organization does not need to have theelectronic-watermark methods unique to all organizations from thebeginning. When the used embedding organization is identified byelectronic-watermark information obtained by the commonelectronic-watermark method, it is possible that the united monitoringorganization asks the embedding organization to send the extractingmeans employing the electronic-watermark method unique to theorganization and its key.

(Third Embodiment)

FIG. 5 shows a portion related to electronic-watermark extractingcorresponding to the electronic-watermark embedding shown in FIG. 1 orFIG. 3.

In FIG. 5, organizations 501 to 504 have the common-electronic-watermarkextracting apparatuses 205, corresponding to thecommon-electronic-watermark embedding apparatus 105, and the type-A totype-D electronic-watermark extracting apparatuses 206 to 209,corresponding to the type-A to type-D embedding apparatuses 106 to 109employing the electronic-watermark methods unique to the organizations,respectively.

An electronic-watermark extracting procedure to be executed in FIG. 5will be described below.

Each of the organizations 501 to 504 monitors data distributed or usedon the network 210. If data which seems to be an illegitimate copy isfound or reported in the network, the organization extracts informationembedded by the common electronic-watermark method, by the use of thecommon-electronic-watermark extracting apparatus 205. With thisoperation, the organization which embedded the information or the usedmethod is identified. When it is determined that the organizationemploys the used method, it extracts information by theelectronic-watermark extracting apparatus unique to the organization.When it is determined that another organization employs the used method,a notice is sent to the organization or the obtained information isdiscarded, according to conditions.

In the system according to the present embodiment, illegitimate copyingcan be monitored without having a united monitoring organization. Thissystem can be applied to either of the embedding systems shown in FIG. 1and FIG. 3. It is also clear that the extracting systems shown in FIG. 2and FIG. 4 can be applied to either of the embedding systems shown inFIG. 1 and FIG. 3.

The system shown in FIG. 5 can be combined with that shown in FIG. 2 andthat shown in FIG. 4. When the organization 200 according to the firstembodiment shown in FIG. 2 has all of the type-A to type-Delectronic-watermark extracting apparatuses as the organization 400according to the second embodiment, and the organizations 201 and 202have the common-electronic-watermark extracting apparatuses 205 in thesame way as in the third embodiment, for example, the organizations 203and 204, which do not have the common-electronic-watermark extractingapparatus 205, execute the same processing as in the first embodiment,and the organizations 200, 201, and 202 can extract electronic-watermarkinformation by the use of the common-electronic-watermark extractingapparatuses 205 within their organizations as in the second and thirdembodiments.

With the above cases being included, the present invention includes alltechniques in which the common-electronic-watermark method having a highrobustness and an electronic-watermark method unique to eachorganization are used according to conditions.

(Fourth Embodiment)

In the embedding systems shown in FIG. 1 and FIG. 3, it is possible thateach organization has the electronic-watermark extracting apparatuscorresponding to the electronic-watermark embedding apparatus and anelectronic-watermark extracting check is performed beforeelectronic-watermark embedding.

This configuration can be applied to the first embodiment, the secondembodiment, and a combination thereof. A fourth embodiment will bedescribed below by referring to FIG. 6 with the embodiment shown in FIG.3 being taken as an example.

In FIG. 6, a common-electronic-watermark embedding organization 600includes the common-electronic-watermark embedding apparatus 105 and thecorresponding common-electronic-watermark extracting apparatus 205.Organizations 601 to 604 have the type-A to type-D electronic-watermarkembedding apparatuses 106 to 109 employing the electronic-watermarkmethods unique to the organizations and the corresponding the type-A totype-D electronic-watermark extracting apparatuses 206 to 209.

Each of the organizations 601 to 604 registers a copyrighted material atthe organization 600 and asks it to embed information by the use of thecommon-electronic-watermark embedding apparatus 105. The organization600 checks whether the copyrighted material is not an illegitimate copyby the use of the common-electronic-watermark extracting apparatus 205before using the common-electronic-watermark embedding apparatus 105.When it is determined by the common-electronic-watermark extractingapparatus 205 that the common electronic watermark has been embedded inthe copyrighted material, the organization 600 asks theembedding-request-source organization or the organization identified bythe electronic-watermark information if there is no problem. When thereis no problem, the organization 600 sends back predetermined informationto the embedding-request-source organization by thecommon-electronic-watermark embedding apparatus 105. Theembedding-request-source organization embeds various types ofinformation by the use of the electronic-watermark embedding apparatus,one of the apparatuses 106 to 109.

According to the system of the present embodiment, electronic-watermarkoverwriting caused by an illegitimate report of a requester can beprevented. In addition, an efficient system is implemented because anelectronic-watermark embedding organization and an electronic-watermarkextracting organization are integrated as a unit.

A recording medium according to another embodiment of the presentinvention will be described below.

The present invention is not limited to cases in which the systems andthe apparatuses described in the above embodiments are combined. Thepresent invention also includes cases in which a software program codefor implementing each of the above embodiments is sent to the systems orthe computers (CPUs or MPUs) of the apparatuses and the systems or thecomputers of the apparatuses operate the above-described various devicesaccording to the program code to implement each of the aboveembodiments.

In these cases, the program code of the software itself implements thefunctions of the above embodiments. Therefore, the present inventionincludes the program code itself, and means for sending the program codeto a computer, specifically, a recording medium for storing the programcode.

As recording media for storing the program code, semiconductor memoriessuch as ROMs and RAMs, floppy disks, hard disks, optical disks,magneto-optical disks, CD-ROMS, magnetic tape, and non-volatile memorycards can be used.

The present invention includes the program code not only in cases inwhich the computers control various devices only according to the sentprogram code to implement the functions of the above-describedembodiments, but also in cases in which the program code implements theabove-described embodiments together with the operating systemsoperating on the computers or with other application software programs.

The present invention also includes a case in which a program code isstored in a memory provided for a function extending board or a functionextending unit connected to a computer; a CPU provided for the functionextending board or the function extending unit executes a part or thewhole of actual processing; and the above-described embodiments areimplemented by the processing.

As described above, according to the above embodiments, even in a systemwhich uses different electronic-watermark methods, a monitoringorganization efficiently monitors illegitimate copying without havingmany electronic-watermark embedding apparatuses and manyelectronic-watermark Improved safety is provided in case in which anelectronic watermark is not found, as compared with a case in which eachelectronics watermark method is used alone.

1. An information processing system in which a plurality of informationprocessing apparatuses are connected through a network, at least one ofthe plurality of information processing apparatuses comprising: firstadding means for adding first additional information to inputinformation as an electronic watermark using a first adding method; andsecond adding means for adding second additional information to theinput information as an electronic watermark using a second addingmethod, wherein the first adding method has a higher robustness than thesecond adding method and wherein the first additional information can beused for identifying the second adding method.
 2. An informationprocessing system according to claim 1, further comprising communicationmeans for communicating among the plurality of information processingapparatuses when said first adding means and said second adding meansare provided for different information processing apparatuses.
 3. Aninformation processing system according to claim 1, wherein the firstadditional information can be used for identifying each informationprocessing apparatus on the network.
 4. An information processing systemaccording to claim 1, wherein the second adding method is different fromthe first adding method.
 5. An information processing system accordingto claim 1, wherein the second additional information is unlikely toreduce the quality of the input information or is information whichpeople are unlikely to perceive.
 6. An information processing systemaccording to claim 1, wherein the second additional information islarger in amount than the first additional information.
 7. Aninformation processing system according to claim 1, wherein the secondadding method is the same as the first adding method.
 8. An informationprocessing system according to claim 1, wherein the first adding methoduses confidential information common to the plurality of informationprocessing apparatuses.
 9. An information processing system according toclaim 8, wherein the confidential information is the position of thefirst additional information or the amount of change against the firstadditional information.
 10. An information processing system accordingto claim 1, wherein the information processing apparatus furthercomprises first and second extracting means for extracting the first andsecond additional information, respectively, from the input informationto which the first and second additional information has been added. 11.An information processing system according to claim 10, wherein, beforeadditional information is added to the input information by the use ofsaid first or second adding means, whether additional information hasbeen added to the input information is checked by the use of the firstor second extracting means corresponding to the first or second addingmeans.
 12. An information processing system in which a plurality ofinformation processing apparatuses are connected through a network, atleast one of the plurality of information processing apparatusescomprising: first extracting means for extracting first additionalinformation added as an electronic watermark using a first adding methodfrom input information by a first extracting method; and secondextracting means for extracting second additional information added asan electronic watermark using a second adding method from the inputinformation by a second extracting method identified by the extractedfirst additional information; wherein the first adding method has ahigher robustness than the second adding method and wherein the firstadditional information can be used for identifying the second addingmethod.
 13. An information processing system according to claim 12,further comprising communication means for communicating among theplurality of information processing apparatuses when said first addingmeans and said second adding means are provided for differentinformation processing apparatuses.
 14. An information processing systemaccording to claim 12, wherein the information processing apparatusfurther comprises determination means for determining that an attack hasbeen made to the input information when only the first or the secondadditional information is extracted, and that the input information hasno additional information when neither the first nor the second additioninformation is extracted.
 15. An information processing apparatuscomprising: first adding means for adding first additional informationto input information at a high robustness as an electronic watermarkusing a first adding method; and second adding means for adding secondadditional information to the input information as an electronicwatermark using a second adding method and wherein the first additionalinformation can be used for identifying the second adding method.
 16. Aninformation processing apparatus according to claim 15, wherein thesecond adding method is different form the first adding method.
 17. Aninformation processing apparatus according to claim 15, wherein thesecond additional information is unlikely to reduce the quality of theinput information or is information which people are unlikely toperceive.
 18. An information processing according to claim 15, whereinthe second additional information is larger in amount than the firstadditional information.
 19. An information processing apparatusaccording to claim 15, wherein the second adding method is the same asthe first adding method.
 20. An information processing apparatusaccording to claim 15, wherein the first adding method uses confidentialinformation common to the plurality of information processingapparatuses on the network.
 21. An information processing apparatusaccording to claim 20, wherein the confidential information is theposition of the first additional information or the amount of changeagainst the first additional information.
 22. An information processingapparatus according to claim 15, further comprising first and secondextracting means for extracting the first and second additionalinformation, respectively, from the input information to which the firstand second additional information has been added.
 23. An informationprocessing apparatus according to claim 22, wherein, before additionalinformation is added to the input information by the use of said firstor second adding means, whether additional information has been added tothe input information is checked by the used of the first or secondextracting means corresponding to the first or second adding means. 24.An information processing apparatus comprising: first extracting meansfor extracting first additional information added as an electronicwatermark using a first adding method from input information from inputinformation by a first extracting method; and second extracting meansfor extracting second additional information added as an electronicwatermark using a second adding method from the input information by asecond extracting method identified by the extracted first additionalinformation; wherein the first adding method has a higher robustnessthan the second adding method and wherein the first additionalinformation can be used for identifying the second adding method.
 25. Aninformation processing apparatus according to claim 24, furthercomprising determination means for determining that an attack has beenmade to the input information when only the first or the secondadditional information is extracted, and that the input information hasno additional information when neither the first nor the secondadditional information is extracted.
 26. An information processingmethod comprising: a first adding step of adding first additionalinformation to input information at a high robustness as an electronicwatermark using a first adding method; and a second adding step ofadding second additional information to the input information as anelectronic watermark using a second adding method and wherein the firstadditional information can be used for identifying the second addingmethod.
 27. An information processing method comprising: a firstextracting step of extracting first additional information added as anelectronic watermark using a first adding method from input informationby a first extracting method; and a second extracting step of extractingsecond additional information added as an electronic watermark using asecond adding method from the input information by a second extractingmethod; wherein the first adding method has a higher robustness than thesecond adding method and wherein the first additional information can beused for identifying the second adding method.
 28. An informationprocessing method according to claim 27, further comprising adetermination step of determining that an attack has been made to theinput information when only the first or the second additionalinformation is extracted, and that the input information has noadditional information when neither the first nor the second additionalinformation is extracted.
 29. A computer-readable recording medium forstoring a program, the medium embodying a program comprising: a firstadding step of adding first additional information to input informationas an electronic watermark using a first adding method having a highrobustness; and a second adding step of adding second additionalinformation as an electronic watermark using the input information usinga second adding method, wherein the first additional information can beused for identifying the second adding method.
 30. A computer-readablerecording medium for storing a program, the medium embodying a programcomprising: a first extracting step of extracting first additionalinformation added as an electronic watermark using a first adding methodfrom input information; an identifying step of identifying an extractingmethod by the extracted first additional information; and a secondextracting step of extracting second additional information added as anelectronic watermark using a second adding method from the inputinformation by the identified extracting method wherein the first addingmethod has a higher robustness than the second adding method and whereinthe first additional information can be used for identifying the secondadding method.